vec3.h

#ifndef VEC3_H
#define VEC3_H

#include "math.h"
#include <iostream>

class vec3 {
    public:
        __host__ __device__ vec3() : e{0.0f,0.0f,0.0f} {}
        __host__ __device__ vec3(float e0, float e1, float e2) : e{e0, e1, e2} {}

        __host__ __device__ float x() const { return e[0]; }
        __host__ __device__ float y() const { return e[1]; }
        __host__ __device__ float z() const { return e[2]; }

        __host__ __device__ vec3 operator-() const { return vec3(-e[0], -e[1], -e[2]); }
        __host__ __device__ float operator[](int i) const { return e[i]; }
        __host__ __device__ float& operator[](int i) { return e[i]; }

        __host__ __device__ vec3& operator+=(const vec3 &v) {
            e[0] += v.e[0];
            e[1] += v.e[1];
            e[2] += v.e[2];
            return *this;
        }

        __host__ __device__ vec3& operator*=(const float t) {
            e[0] *= t;
            e[1] *= t;
            e[2] *= t;
            return *this;
        }

        __host__ __device__ vec3& operator/=(const float t) {
            return *this *= 1/t;
        }

        __host__ __device__ float length() const {
            return sqrt(length_squared());
        }

        __host__ __device__ float length_squared() const {
            return e[0]*e[0] + e[1]*e[1] + e[2]*e[2];
        }

		__device__ inline static vec3 random(curandState* rand_state) {
			return vec3(random_float(rand_state), random_float(rand_state), random_float(rand_state));
		}

		__device__ inline static vec3 random(float min, float max, curandState* rand_state) {
			return vec3(random_float(min, max, rand_state), random_float(min, max, rand_state), random_float(min, max, rand_state));
		}

		__host__ __device__ bool near_zero() const {
			// Return true if the vector is close to zero in all dimensions.
			const float s = 1e-8f;
			return (fabs(e[0]) < s) && (fabs(e[1]) < s) && (fabs(e[2]) < s);
		}

    public:
        float e[3];
};

// Type aliases for vec3
using point3 = vec3;   // 3D point
using color = vec3;    // RGB color

// vec3 Utility Functions

__host__ inline std::ostream& operator<<(std::ostream &out, const vec3 &v) {
    return out << v.e[0] << ' ' << v.e[1] << ' ' << v.e[2];
}

__host__ __device__ inline vec3 operator+(const vec3 &u, const vec3 &v) {
    return vec3(u.e[0] + v.e[0], u.e[1] + v.e[1], u.e[2] + v.e[2]);
}

__host__ __device__ inline vec3 operator-(const vec3 &u, const vec3 &v) {
    return vec3(u.e[0] - v.e[0], u.e[1] - v.e[1], u.e[2] - v.e[2]);
}

__host__ __device__ inline vec3 operator*(const vec3 &u, const vec3 &v) {
    return vec3(u.e[0] * v.e[0], u.e[1] * v.e[1], u.e[2] * v.e[2]);
}

__host__ __device__ inline vec3 operator*(float t, const vec3 &v) {
    return vec3(t*v.e[0], t*v.e[1], t*v.e[2]);
}

__host__ __device__ inline vec3 operator*(const vec3 &v, float t) {
    return t * v;
}

__host__ __device__ inline vec3 operator/(vec3 v, float t) {
    return (1/t) * v;
}

__host__ __device__ inline float dot(const vec3 &u, const vec3 &v) {
    return u.e[0] * v.e[0]
         + u.e[1] * v.e[1]
         + u.e[2] * v.e[2];
}

__host__ __device__ inline vec3 cross(const vec3 &u, const vec3 &v) {
    return vec3(u.e[1] * v.e[2] - u.e[2] * v.e[1],
                u.e[2] * v.e[0] - u.e[0] * v.e[2],
                u.e[0] * v.e[1] - u.e[1] * v.e[0]);
}

__host__ __device__ inline vec3 unit_vector(vec3 v) {
    return v / v.length();
}

__device__ vec3 random_in_unit_sphere(curandState* local_rand_state) {
    while (true) {
        vec3 p = vec3::random(-1,1,local_rand_state);
        if (p.length_squared() >= 1) continue;
        return p;
    }
}

__device__ vec3 random_unit_vector(curandState* local_rand_state) {
    return unit_vector(random_in_unit_sphere(local_rand_state));
}

__device__ vec3 random_in_hemisphere(const vec3& normal, curandState* local_rand_state) {
    vec3 in_unit_sphere = random_in_unit_sphere(local_rand_state);
    if (dot(in_unit_sphere, normal) > 0.0) // In the same hemisphere as the normal
        return in_unit_sphere;
    else
        return -in_unit_sphere;
}

__device__ vec3 reflect(const vec3& v, const vec3& n) {
	return v - 2 * dot(v, n) * n;
}

__device__ vec3 refract(const vec3& uv, const vec3& n, float etai_over_etat) {
    float cos_theta = fmin(dot(-uv, n), 1.0f);
    vec3 r_out_perp =  etai_over_etat * (uv + cos_theta*n);
    vec3 r_out_parallel = -sqrt(fabs(1.0f - r_out_perp.length_squared())) * n;
    return r_out_perp + r_out_parallel;
}

__device__ vec3 random_in_unit_disk(curandState* local_rand_state) {
    while (true) {
        vec3 p = vec3(random_float(-1.0f,1.0f,local_rand_state), random_float(-1.0f,1.0f,local_rand_state), 0.0f);
        if (p.length_squared() >= 1) continue;
        return p;
    }
}

#endif